It has almost become a Christmas tradition, albeit one wrapped in a curse: the X Factor final takes place in late December, and the winner releases a single which goes on to become the festive chart topper.

Almost, because only once in the last six years has it not happened – in 2009, when a concerted campaign against the programme saw Rage Against the Machine's Killing in the Name pinch the top spot from winner Joe McElderry. And a curse because, more often than not, the winner then fades into chart obscurity.

What future awaits Little Mix, this year's winners, has yet to be decided. Although their song went to No 1 in the singles chart on Sunday, bookmakers' odds (12-1) suggest it won't be there on Christmas Day. Instead, a 100-strong choir led by Gareth Malone and made up of the wives of servicemen on tour in Afghanistan is the favourite (1-10) after achieving a record number of preorders for their song Wherever You Are.

But there is still hope for Little Mix, and indeed the other past X Factor winners and nearly-rans who were either voted off the show or faded into chart obscurity. Several former contestants of Simon Cowell's talent shows, many of whose pop careers spluttered out prematurely, have found a more sustainable second career treading the boards of stage musicals in London's West End.

This week it was announced that Shayne Ward, who won The X Factor in 2005, had extended his contract as the star of jukebox musical Rock of Ages until September 2012. Round the corner, Darius Campbell, who appeared in Pop Idol and Pop Stars under his former surname Danesh, is coming to the end of his third stint as Billy Flynn in Chicago. Brenda Edwards, an X Factor semifinalist the same year as Ward, is currently starring as the Killer Queen in We Will Rock You, while a gala performance of Children of Eden next month boasts Gareth Gates and John Wilding as Cain and Abel. Gates was a Pop Idol runner-up in 2002; Wilding has been in The X Factor two years running, eliminated both times at the "judges' houses" stage.

"At the moment, X Factor contestants either seem to go into the theatre or ITV2," said Peter Robinson, editor of pop website Popjustice. "Like eBay being flooded with iPhone 3GSs because they've brought out a new one, everyone's picking up X Factor stuff from two years ago, and the West End is a part of that."

Producer Mark Rubinstein, president of West End trade association the Society of London Theatre, is relaxed about the influx of Cowell's acts: "Anything that encourages people to come to the theatre has got to be a good thing. Audiences have always wanted stars – that's what the West End is about. In the last three years, the West End has reported groundbreaking figures." Despite the recession, 14.1m tickets were sold in 2010, earning £512m, up from £505m in 2009.

Andrew Panton, associate head of performance in musical theatre at the Royal Conservatoire of Scotland, disagreed: "There's already a reduction in the quality of the shows. Saturday night TV can provide a quick way of putting bums on seats in the short term, but in the long term it stops trained people getting jobs."

Only training, Panton believes, can adequately prepare a performer for doing eight shows a week. "I've seen [the role of] Marius in Les Mis absolutely massacred by a pop artist recently. We're talking about a big, classic musical and we're putting in pop voices that can't handle it." The role was recently played by Gates and Nick Jonas of the Jonas Brothers.

The first West End musical routinely to cast TV and film stars was Chicago, in which Campbell first starred in 2005. Other talent-show contestants to make the transition to musicals include X Factor alumni Diana Vickers in The Rise and Fall of Little Voice, TreyC Cohen in The Wiz, Niki Evans in Blood Brothers, and Lucie Jones in Les Miserables.

Britain's Got Talent, another Cowell show, has also inspired a musical in the unlikely shape of I Dreamed a Dream, based on the life of Susan Boyle, which opens in Newcastle in March. Boyle is played by Elaine C Smith, but will perform in person at the show's climax.

Joanna Read, principal of drama school Lamda, doesn't believe this casting is a theatrical trend: "It's the equivalent of variety-show casting, when you put Cilla Black in a panto in the 60s. X Factor people are being cast within a very narrow range of shows. If you look at the children in Matilda, they are fantastically trained – you couldn't walk in off the streets and play that role."

Robinson believes this year's X Factor finalists contain potential West End stars. "I'd love to see 2 Shoes, maybe both playing the same part on stage," he says of the Essex duo ejected in the first week. "Janet Devlin could do a run at Little Voice. Marcus Collins and Amelia Lily have both got the required star quality. Kitty Brucknell's more cabaret."

Yet the even the most successful West End stars are reluctant to turn their backs on pop: both Campbell and Ward maintain that they will go back to making records, despite waning public interest. "This wasn't my first choice," says Ward of his stage role, "but I get acting experience – it's a great platform." Campbell, meanwhile, will perform Chicago on Broadway next year. "Irrespective of anything I told Simon Cowell 10 years ago, these are things I managed to achieve on my own two feet. Hopefully he'll be in the audience on Broadway."

Wives favourite

The song that is likely to take the No 1 spot in the singles chart this Christmas is by Military Wives with Gareth Malone, who perform Wherever You Are.

The song, written by Paul Mealor, who composed music for April's royal wedding, is set to a poem compiled from letters to and from the servicemen and their partners during a six-month tour of duty in Afghanistan. The women were persuaded to join a choir developed by Gareth Malone, who visited military bases in Chivenor and Plymouth. Bookmakers William Hill have the Military Wives choir at 1/8, with X Factor winners Little Mix far behind them at 12/1.

Louise Ringrose, spokesperson for Decca Records, which is releasing the track – the proceeds of which will raise funds for military charities including the Royal British Legion and SSAFA Forces Help – said: "A lot of people are finding something in the lyrics and the music that strikes a chord with them. This isn't a fight against X Factor but a celebration of what military service people and their partners sacrifice."

The eventual winner of this year's 60th official Christmas No 1 will become the first recipients of a new award from the Official Charts Company when the result is announced on Christmas Day, with each artist who makes it to the top of the charts given a trophy marking the achievement throughout the year. Alexandra Topping